The GNU Compiler Collection contains frontends for
C, C++, Objective-C, Fortran, Java, and Ada as
well as libraries for these languages. It is a
full-featured ANSI C compiler with support for K&R
C as well. GCC provides many levels of source code
error checking traditionally provided by other
tools (such as lint), produces debugging
information, and can perform many different
optimizations to the resulting object code.

Linux is a clone of the Unix kernel, written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX and Single UNIX Specification compliance. It has all the features you would expect in a modern fully-fledged Unix kernel, including true multitasking, virtual memory, shared libraries, demand loading, shared copy-on-write executables, proper memory management, and TCP/IP networking.

PHP is a widely-used Open Source general-purpose scripting language that is especially suited for Web development and can be embedded into HTML. Its syntax draws upon C, Java, and Perl, and is easy to learn. PHP runs on many different platforms and can be used as a standalone executable or as a module under a variety of Web servers. It has excellent support for databases, XML, LDAP, IMAP, Java, various Internet protocols, and general data manipulation, and is extensible via its powerful API. It is actively developed and supported by a talented and energetic international team. Numerous Open Source and commercial PHP-based application packages are available.

Clam AntiVirus is an anti-virus toolkit designed especially for email
scanning on mail gateways. It provides a number of utilities, including
a flexible and scalable multi-threaded daemon, a commandline scanner,
and a tool for automatic database updates. The core of the package is an
anti-virus engine available as a shared library.

Wireshark is a network protocol analyzer, or "packet sniffer", that lets you capture and interactively browse the contents of network frames. It provides a commercial-quality packet analyzer for Unix, and the most useful packet analyzer on any platform.

VLC media player is a multimedia player, framework, streamer, and encoder. It can play inputs like files, network streams, DVDs, audio CDs, Blu-Rays, capture devices, and screens. It can play most audio and video codecs and formats (MPEG 1/2/4, H264, VC-1, DivX, WMV, Vorbis, AC3, AAC, MKV, etc.), but can also be used to convert to different formats and/or send streams through the network.

ZABBIX is an enterprise-class distributed monitoring solution designed to monitor and track performance and availability of network servers, devices, and other IT resources. It supports distributed and Web-based monitoring, auto-discovery, real-time monitoring, SLA assurance, trending, and more.

fio is an I/O tool meant to be used both for benchmark and stress/hardware verification. It has support for 19 different types of I/O engines (sync, mmap, libaio, posixaio, SG v3, splice, null, network, syslet, guasi, solarisaio, and more), I/O priorities (for newer Linux kernels), rate I/O, forked or threaded jobs, and much more. It can work on block devices as well as files. fio accepts job descriptions in a simple-to-understand text format. Several example job files are included. fio displays all sorts of I/O performance information, including complete IO latencies and percentiles. Fio is in wide use in many places, for both benchmarking, QA, and verification purposes. It supports Linux, FreeBSD, NetBSD, OpenBSD, OS X, OpenSolaris, AIX, HP-UX, Android, and Windows.

Python is an interpreted, interactive,
object-oriented programming language. It combines
remarkable power with very clear syntax, and isn't
difficult to learn. It has modules, classes,
exceptions, very high level data types, and
dynamic typing. There are interfaces to many
system calls and libraries, as well as to various
windowing systems (Tk, Mac, MFC, GTK+, Qt,
wxWindows). New built-in modules are easily
written in C or C++. Python is also usable as an
extension language for applications that need a
programmable interface.